DE10009952A1 - Formation of toner layer for electrophotographic printer, copier, facsimile, by control of physical and mechanical parameters and control of electrical characteristics of developer - Google Patents

Abstract

Non-magnetic, one component developer of average volume particle diameter (D) is charged to average specific charge (q/m) and charged developer fed to developer roller which has surface roughness (Rz). Layer of developer is formed with thickness (dt) on developer roller using metal blade in contact with developer roller with blade pressure (Pb) to fulfill relationship: 4 <= D <= 12; 5 <= q/m <= 12; 1 <= Rz <= 12; 20 <= Pb <= 80; dt = 1.8 asterisk (q/m asterisk Rz/(Pb-1)) \2 asterisk D +- 0.24 D and 1.5 D <= dt <= 3.5 D. Independent claim included for non-magnetic and one component developer for non contact developing, container for developer,

Description

BACKGROUND OF THE INVENTION

The present invention relates generally to Ent developers, development processes, development devices and its elements and imaging devices, and in especially a non-magnetic and one-component device winder, a development process in which the non-magnetic tables and one-component developer is used, a Development roller, a blade that is a thickness of a layer made of non-magnetic and one-component developer at the Development role regulates a process for forming a Layer of non-magnetic and one-component developer using the blade, a developing device with the development roller and the blade and an electro photographic imaging device with one or several of these elements. The present invention is for Example suitable for a color laser printer.

Hereinafter referred to the "non-magnetic and on component developer "a one component developer who is not magnetized and contains no carrier. The "Electrophotographic imaging device", the typi is usually a non-impact printer Printer that provides a recording by a developer ler as a recording material on a recording medium (e.g. printing paper and OHP film) is deposited.

Along with the recent development of the office car The use of electrophotography has become more difficult imaging devices such as a laser printers for computer output devices, facsimile machines NEN, copier, etc., constantly spread. With the electro photographic process generally comes a photoconductive ger insulator (photosensitive drum) and he  contains the steps for loading, exposing, developing, Transferring, fixing and other post processes.

The loading step turns the photosensitive drum uniformly electrified (e.g. to -600 V). With the Be a laser beam, etc., on the photo irradiated sensitive drum and the electric poten tial on the irradiated area, for example to about -50 V degraded, creating an electrostatic latent image is produced. In the development step, the developer for example on the photosensitive drum Using a reverse process, electrically separated and made the electrostatic latent image visible. The Reversal process is a development process in which a electric field due to a development bias in Areas where the electrical charge is formed by the Exposure is eliminated, and the developer doing the same Polarity like uniformly charged areas on the photosensitive drum abge by the electric field will be divorced. In the transfer step, a toner becomes image that corresponds to the electrostatic latent image, generated on a recording medium. At the fixing step the toner image is used on the recording medium formation of heat, pressure, etc., melted and fixed where is obtained through a printed matter. The post processes can unloading and cleaning the transferred photosensitive Drum, collecting and recirculating and / or disposal residual toner, etc.

The developer for use in the above Development step can be roughly translated into a developer One component system using the toner and in a developer of a two-component system using the toner and carrier. With the toner a particle can be used, for example is produced in such a way that a coloring sub punch like a dye and carbon black or the like  in a synthetic macromole binder resin kular compound is dispersed and then to a fine Powder of about 3 to 15 microns is ground. A usable one Carrier can be, for example, an iron powder or a ferrite ball of about 100 microns in diameter included. The develop The one-component system advantageously leads (1) to a simple and small developing device Because of elimination of carrier deterioration, one Toner density control, mixing and stirring mechanisms and (2) to used toner without any waste such as a carrier.

The developer of the one-component system can also are classified into a magnetic and single component developer, the toner in a magnetic powder ent holds, and in a non-magnetic and one-component developer who does not contain this. The disadvantages of magnetic and one-component developers, however (1) in the low transmission power due to the high Low electrical magnetic powder content Resistance, causing an increased amount of electrical charge is prevented, (2) in poor coloring due to its weakly transparent, black magnetic powder, (3) in the low fixing power because of the magnetic Powder a high temperature and / or a high pressure requires, which drives up running costs become. It is therefore assumed that the demand for non-magnetic and one-component developer without this Disadvantages will increase in the future.

For non-magnetic and one-component developers usually uses the toner that is relatively high specific volume resistance (e.g. 300 GΩ.cm, etc.). In addition, since the toner is essentially no elec has tric charges, by triboelectricity or Charge injection loaded in the developing device become.  

The development process in which the non-magnetic and one-component developer is used in Kon tact and non-contact development processes divided: at The development process of the contact type is developed deposited on the photosensitive drum by the development role that the developer is on, is brought into contact with the photosensitive drum; and in the development process of the non-contact type a certain gap (e.g. about 350 µm) between the developer tion roll and the photosensitive drum provided to arrange them separately and the developer flies from the development role to the photosensitive Drum and is deposited on it. The disadvantage of Development process of the contact type is that the Developer due to friction between the development role and the photosensitive drum may deteriorate and also cracking in the photosensitive film can be effected, whereby the life of the fotoemp sensitive body is shortened. Accordingly, in the latter Time the development process of the non-contact type in the Moved to the center where this deterioration is not occur.

For the development process of the non-contact type, at that of the non-magnetic and one-component developer for When it comes to use, it is significant that sufficient Image density ensured by controlling the amount of toner is going from the development role to the photosensitive Drum flies. So it is important to use a thin toner layer to form while its thickness is developing role is controlled. As a typical process for regulation a toner layer thickness has conventionally been proposed gene, an elastic blade (limiting blade) in contact with the development roller to provide the layer thickness maintain uniform.  

The development facility at which the development method of the non-contact type with the non-magnetic and One component developer is used, generally includes mean a reset role, a development role and one Blade. The development role is with a bias energy supply and is connected by the preload generator Giezufuhr with the development bias of superimposed AC and DC voltages provided. The back setting roll, also used as a feed roll or application roll the development role: the Reset roller is not only used to develop the toner supply role, but also to the toner that the development was not used and on the development role remains to scrape and remove. The Ent development role that is, for example, a role that is made up of Metal such as aluminum is adsorbed charged toner on their surface in the form of thin Layer and transports it to a development area.

The blade contacts the development role and serves to bring the toner layer to a uniform thickness regulate. The blade can be made from an elastic link like be made of urethane or a metal link Has contact section with the development roller, that of resin is. According to Japanese Patent Publications (Kokai) Nos. 8-202130 and 6-102748, for example, when a Me tall limb, namely a rigid limb, for development role is used, the toner layer is regulated, by a blade made up of an elastic body such as Rubber is brought into contact with the development role becomes; if on the other hand a link from an elastic Bodies such as rubber for a surface of development role is used, the toner layer can be regulated by adding an end portion or non-end portion (namely a middle section) in contact with the development role brought. To damage the development role  and to avoid the blade by the accuracy of the Contact pressure is weakened at the contact portion is required between them at this level Technique the use of a contact between one that is rigid, and the other, which is elastic, is conceived been. Japanese Patent Publications (Kokai) Nos. 8-202130 and 6-102748 also disclose surface roughness development role, a pressure with which the blade is pressed against the development role (blade pressure), a toner particle diameter and other conditions for Form a toner layer as shown in the table below 1 are shown.

TABLE 1

In operation, the toner is separated by sliding friction the reset roller, the blade and the development roller loaded (e.g. negative). The negatively charged toner will then a surface of the development role through the Reset roller fed and then electrostatic Adsorption deposited. Then the toner layer leveled on the development roller by the blade to a thin layer with a uniform thickness of about 10 µm to form up to 40 µm. The toner that is developing area where a surface of the Development role closest to the photosensitive role flies under with the electrical attraction Using a predetermined voltage on the Ent applied to an electrostatic latent image on the photosensitive drum and adheres on him. As a result, the latent image is made visible and developed. Next, the reset roller removes the remaining toner on the development roller, which in a Non-image area is left in which no latent image was generated. In the development process there is a series of these operations repeated.

In the conventional development process of not contact type in which the non-magnetic and one-component However, the developer would use the image quality disadvantageous depending on development conditions worsened. The current inventors have as a result her in-depth study of what makes such a picture deterioration is caused, discovered the image quality of the toner layer formation and the electrical properties tonality.

If it is too thin, the toner layer would become one lead to low and uneven image density while due to a too thick toner layer, a proportion of counter sets charged or low-charged toner would be increased  which creates fog in the non-image area. The current ones Inventors have discovered that toner layer formation is physi calically based on four parameters (although the parameters are not limited to these four) which are surfaces roughness of the development role, a blade pressure, a Toner particle diameter and a charge amount of the toner included, and that these parameters are correct to some extent should be controlled relatively.

The inappropriate surface roughness of the development roll would be an obstacle in forming a uniform Be a toner layer. The surface roughness serves as a mechani force for transporting the toner and as an intermediate link between the development roller and the blade. The If the surface roughness is too small, it would be one Let the toner layer become too thin and reduce the image density then wring out the toner if it is too large layer would become too thick and thereby fog in the Non-image area (i.e., undesirable Coloring an area with no image and the half a white clear room with the toner). If additionally the blade pressure is too low, the Toner layer thickness can not be regulated locally, and the Toner would easily escape the blade. If the Blade pressure is too high, the toner would be so stressed to to create a fusion of toner on the blade, and that Toner loading would likely deteriorate. The toner layer thickness would match the toner particle diameter vary. Furthermore, if the amount of toner charge is too large is, the reflectivity would be in the form of electrical The attraction of the toner on the developing roller increases and the toner layer would become thick. As result an increase in the blade pressure would be a mechanical one Increase the stress on the toner and thereby the toner tend to deteriorate. If the amount of toner charge in the Contrary to this is too small, the electric attraction would  force would be small, and the toner layer would be thin become. As a result, the blade pressure should be kept low be, but this would cause the toner to run out gives way.

Furthermore, the present inventors have discovered that the formation of the toner layer mechanically also depends on (but is not limited to) a blade shape and a toner flow between the reset roller and the development roller. Consider, for example, a conventional developing device 1, a blade 2, a metal plate 2 a, and a rubber plate 2 b includes that adheres to the metal plate 2 a, and roll 4 b by the rubber plate 2 comes into contact with a development such as shown in Fig. 8. Here, Fig. 8 is a partially enlarged sectional view of the developing device 1 using the conventional non-magnetic and one-component toner T. From Fig. 8 it can be seen that in the conventional developing device 1, a toner agglomeration TB is disadvantageously generated at the upper end of the blade 2 . The toner agglomeration TB occurs when the upper end of the blade blocks the flow between the reset roller (not shown) and the development roller 4 , as shown by an arrow.

This toner agglomeration TB can locally apply the pressure between the blade 2 and the developing roller 4 and would cause the excess toner T past the blade 2 to the developing roller 4 , or in the opposite part prevent the correct amount of toner T. comes to the blade 2 . As a result, as shown in Fig. 9, the uniform toner layer may not be formed. Here, Fig. 9 is a partially schematic cross-sectional view showing a state of the developing roller 4 and the toner layer TL formed thereon. A failure to form a uniform toner layer would result in degradation in image quality such as uneven density and white clear space as described above. Although the present inventors b the processing of the rubber plate 2 (z. B. To a bevel) to such a form have considered that does not prevent the toner from flowing, they have discovered that the rubber plate 2 b of a complex shape, which in their shape is slightly curved and changed, the difficulty in forming a uniform toner layer TL increases. In addition, a blade made of an elastic member generally has such disadvantages as difficult to manufacture, low durability, and high manufacturing cost.

Regarding the electrical properties of the toner on the other hand, the present inventors have the specific Volume resistance of the toner is paying attention. The present inventors experimentally have a completed picture (such an image with the entire printable area completely filled out) using commercially available or experimentally produced toners that have different resistance values. The current inventors discovered that regardless of whether the toner has a uniform layer in thickness, which Use of some toners that have certain resistance values have one in developing the non-contact type black or, if printing with multiple colors, a different colored stripe in the paper feed direction generated, which deteriorated the image quality. The current inventors have assumed that this is why occurred because of a high resistance value of the toner moderate toner charging, resulting in a dielectric breakdown would result in the toner, causing irregular streaks are caused.

BRIEF SUMMARY OF THE INVENTION

That is why it is a typical general task of present invention, a new and useful development  ler, a development process, a development device and their elements and an image forming device see one or some of the disadvantages above are eliminated.

Another typical and specific goal of the before lying invention is a developer, a developer development process, a developing device and its ele elements and to provide an image forming apparatus, whereby a high quality image through relatively inexpensive and simple means can be generated stably.

In order to achieve the above objectives, a developer film forming method according to one aspect of the present invention comprises the steps of: loading non-magnetic and one-component developer having an average volume particle diameter D (µm) to an average specific charge q / m (µC / g), feeding the loaded developer to a development roller having a ten-point surface roughness Rz (µm), and forming a layer of a one-component developer with a layer thickness dt (µm) on the development roller by providing a blade in contact with the development roller at one Blade line pressure Pb (gf / cm), where dt, Pb, q / m and D correspond to the following relationships: 4 ≦ D ≦ 12, 5 ≦ q / m ≦ 12, 1 ≦ Rz ≦ 12, 20 ≦ Pb ≦ 80, dt = 1.8 × {q / m × Rz / (Pb-1)} ^1/2 × D ± 0.25D and 1.5D ≦ dt ≦ 3.5D. It has been experimentally confirmed that a developer layer having a uniform thickness can be stably produced according to this developer layer formation method.

A developing device of another aspect of the present invention includes a developing roller having an average ten-point surface roughness Rz (µm) and a blade in contact with the developing roller at a blade line pressure Pb (gf / cm) through which a layer of a non-magnetic and one-component developer is developed has an average volume particle diameter D (µm) and an average specific charge q / m (µC / g), can be formed on the development roller, the layer having a thickness dt (µm) and dt, Pb, q / m and D den correspond to the following relationships: 4 ≦ D ≦ 12, 5 ≦ q / m ≦ 12, 1 ≦ Rz ≦ 12, 20 ≦ Pb ≦ 80, dt = 1.8 × (q / m × Rz / (Pb-1)} ^{1 / 2} × D ± 0.25D and 1.5D ≦ dt ≦ 3.5D It has been shown experimentally that a developer layer having a uniform thickness can be stably formed according to this developing device.

A developing device of another aspect of the The present invention includes a metal development role and a blade that plays the development role in one predetermined blade pressure is contactable to a Layer of a non-magnetic and one-component to educate developers on the development role in which the Blade contains a metal contact section that mates with the Development role is contactable, which contact section has a shape that is selected from a group consisting of acute, curved and round shapes. According to this developing device, the Contact section, which in the shape of a pointed tip Angle, a curvature or a curve, serve to forming a toner agglomeration that causes toner flow blocked from sticking and destroying the toner other.

A developing device of yet another aspect The present invention includes metal development role and a blade with the development role contactable with a blade pressure of 20 to 80 gf / cm is to make a layer of a non-magnetic and income component developer, where the blade is one Contains metal contact portion, which has a surface roughness that is less than a surface roughness of development role is. According to this developing device a toner fusion on the blade by controlling a surface  development roller and blade and roughness Blade pressure can be avoided.

A developer of an aspect of the present invention is for a development process of the non-contact type suitable includes a colored fine particle and a Fluidization agent and has a specific volume resistance stood above about 10 GΩ.cm but less than about 192 GΩ.cm. A container of one aspect of the present invention tion contains the above non-magnetic and one-component ten developer. The non-magnetic and one-component developer has a resistance value that is experimental as was appropriately assessed.

An imaging device of one aspect of the foregoing invention comprises a photosensitive drum, a charger that charges the photosensitive drum, one Exposure part, which is the photosensitive drum, through the charger is charged, exposed and an electrostatic latent image creates a developing device that the exposed photosensitive drum developed and that makes electrostatic latent image visible as a toner image, and a transfer part that applies the toner image drawing medium transfers which developing device any of the developing devices described above includes. This image forming device has the same effect like the above developing devices.

An imaging device as a typical embodiment Form of the present invention includes a photo sensor sensitive drum, a charger that is the photosensitive Drum loads, an exposure part that the photosensitive che drum, which is loaded by the loader, exposed and creates an electrostatic latent image, a development Development device that contains a development role, the removed from the exposed photosensitive drum is arranged, of which development role is not magnetic and one-component developer to the fotoemp  sensitive drum flies, making the photosensitive Drum is developed and the electrostatic latent Image is made visible as a toner image, which developer a volume resistivity of more than about 10 GΩ.cm, but less than 192 GΩ.cm has a transmission part of the toner image on a recording medium carries, and a container that the non-magnetic and One component developer contains. According to this picture The device has the non-magnetic and one-component developer has a resistance value that is experimental was appropriately assessed.

Other objectives and other features of the present Er are readily apparent from the following description of the embodiments with reference to the accompanying Drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a partial main section through a developing device and image forming device of an aspect of the present invention.

Fig. 2 is a graph showing data of Tables 2 to 5.

Fig. 3 is a graph of the data of Tables 6 and 7 shows.

Fig. 4 is a partially enlarged sectional view of another embodiment related to a film formation process by the developing device.

Fig. 5 is a partially enlarged sectional view of another embodiment related to the toner layer formation process by the developing device.

Fig. 6 is a partial schematic cross-sectional view showing a state of a toner layer on a developing roller using the Entwicklungsvorrich processing of Fig. 4 and 5 was formed.

Fig. 7 is a graph showing a relationship between toner resistance values R and vertical stripes.

Fig. 8 is a partially enlarged section through a conventional developing device using a conventional toner layering method.

FIG. 9 is a partially schematic cross section showing a state of a toner layer formed on the developing roller using the developing device of FIG. 8.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Referring now to FIG. 1, a description will now be given of a developing device 100 and an image forming device 200 including the developing device 100 , an aspect of the present invention. Those elements in each figure that are given the same reference numerals designate the same elements, and a duplicate description of them is omitted. Those elements which are provided with the same reference numerals and to which alphabetic capital letters have been added generally denote variants and, unless otherwise specified, are generalized by simple reference numerals without letters. Here, FIG. 1 is a schematic main sectional view of the image forming device 200 having the developing device 100 . The developing device 100 includes a reset roller 10 , a developing roller 20 , a blade 30 , a frame 40, and a developing bias power supply 50 .

I. TONER LAYER FORMATION BY CONTROLLING PHYSICAL PARAMETERS

First, the present inventors have studied the stable forming a toner layer having a uniform thickness on the developing roller 20 to form images with high quality ty to obtain. If the toner layer is too thin, this would result in the disadvantage of low and uneven image density. If the toner layer is too thick, an amount of oppositely charged or low-charged toner would be increased, causing fog formation in non-image areas. The present inventors have discovered, as a result of various experiments to be described later, that formation of a toner layer having a uniform thickness is physically based on four parameters which are a surface roughness of the developing roller, a blade pressure, a toner particle diameter and a toner charge amount included (but not limited to), and that these parameters should be controlled to some extent correlatively. Next is a description of the experiments and their analyzes.

The reset roller 10 , which is also referred to as a feed roller or application roller, contacts the development roller 20 and supplies the development roller 20 with toner T from the frame 40 . The reset roller 10 is made of electrically conductive materials such as sponge to charge the toner T by friction with the developing roller 20 . Fig. 1 in the present embodiment shows that the reset roller 10 rotates to the left (counterclockwise) and is in contact with the developing roller 20 . By this contact and rotation, the toner T is loaded and fed to the developing roller 20 . Furthermore, the reset roller 10 can also serve to collect the remaining toner T that was not used in the development and remained on the development roller 20 . The toner T on the developing roller 20 , if an attempt is made to collect it, is scraped off using the contact between the rollers 10 and 20 and returned to the inside of the frame 40 .

The developing roller 20 adsorbs the toner T on its surface and conveys the toner T as it rotates to the developing area. The developing area is an area where the photosensitive roller 210 and the developing roller 20 , which will be explained later, are closest to each other. For example, the developing roller 20 rotates at the same speed and in the same direction as the photosensitive drum 210 . A usable material for the development roller 20 may include a metal such as aluminum and stainless steel. Applying voltage to these electrically conductive materials allows the toner T to be adsorbed using the electrostatic adsorption. In the present embodiment, an experiment was carried out with an aluminum developing roller 20 having an outer diameter of 20 mm and a stainless steel blade 30 . The test conditions were as follows: a surface roughness of the aluminum development roller was sandblasted with irregularly or regularly (spherically) shaped glass beads as abrasive grains and brought to a predetermined average ten-point roughness Rz. The development roller 20 using these and having the Rz values experimentally varied between 1 µm and 12 µm was manufactured, and an optimal surface roughness was researched.

The blade 30 is a member that serves to limit the toner T supplied by the reset roller 10 to a predetermined thickness, and is made of an elastic body such as typically urethane, etc., a metal that has leaf spring properties has such as stainless steel and bronze. A method of regulating the toner layer TL is different for these materials and includes scraping and pressing. In the present embodiment, as the blade 30, three kinds of links are made of stainless steel plates with different thicknesses of 0.10 mm, 0.12 mm and 1.50 mm, respectively, and brought into contact with the development roller 20 at a predetermined pressure . The blade pressure can be adjusted by changing three factors of a blade plate pressure, a free length corresponding to a distance from a blade holder part to a roller contact portion, and a deflection amount using the following equation 1. In the present embodiment, the blade pressure worked out with the equation 1 was varied in a range of 10 to 100 g / cm, and the optimal value was determined.

W is a total load of the blade pressure, δ a Amount of deflection, E a modulus of elasticity, b a blades width, h a plate thickness and L a free length.

The frame contains the toner T, it leads the reset roller 10 and takes up toner that has been collected by the reset roller 10 . The frame 40 contains a paddle, a stirrer and other components (not shown) and is connectable to an external toner reservoir, such as a toner cartridge. The bias power supply 50 includes superimposed AC / DC power supplies.

The toner was made from non-magnetic and one-component selected developers who are commonly used and manufactured by, for example, fine carbon particles as a dye and a charge control agent with a Polyester resin were kneaded and made to a predetermined one pulverized average volume particle diameter were. Optionally, for the toner T, if necessary, an elongation inhibitor made of low molecular material such as such as wax, polyethylene and polypropylene can be used (to be contained in it). Powder smaller than 3 µm and coarse particles that were equal to or larger than 20 µm,  were then removed and attached to the remaining particles fine particles of silicon oxide and titanium oxide became external deposited and applied to their surface to form a Provide fluidity and charge. This toner has T such thermal characteristics that its glass over transition temperature between 55 and 67 ° C and its melting point is between 120 and 150 ° C. A great distance between the glass transition temperature and melting point is on its wide range of coating ratio of external attachments, a molecular distribution and one Degree of crosslinking of styrene resin. In which Experiment, the toner T was used to pass through had an average volume particle diameter of 7.5 µm. The toner T can not only by the above Powdering process can be obtained, but also under Use any preferred method such as one Polymerization process, a spray drying process and other powder manufacturing processes.

The charge amount of the toner T was determined by measuring a state of the toner layer TL on the developing roller 20 using the E-Spart analyzer (manufactured by Hosokawa Micron Corporation). The most desirable specific toner charge q / m in terms of toner layering and image quality is -5 µC / g to -30 µC / g. A specific toner charge of less than -5 µC / g would thin the toner layer due to its low reflectivity in the form of an attractive force on the developing roller 20 and prevent the toner from developing constantly through the gap between the developing roller 20 and the photosensitive drum 210 flows at the development bias, thereby reducing the image density. In contrast, a specific toner charge q / m in excess of -30 µC / g would increase its reflectivity and reduce the development effectiveness. Furthermore, since the higher specific charge would make the regulation of the toner difficult, the surface roughness of the development roller 20 must be small while the blade pressure must be high.

In the experiment, the reset roller 10 was brought into contact with the developing roller 20 with the contact depth of 1 mm, and the two rollers were rotated to the left. As a result, the reset roller 10 and the developing roller 20 were rotated in opposite directions at their contact point. The reset roller 10 , which had such a structure in the form of a metal shaft coated with a urethane foam having a conductivity, had an outer diameter of 20 mm and a resistance of 10 ⁷ Ω between the shaft and the foam. The rotational speed of both the reset roller 10 and the developing roller 20 was set to 90 mm / s.

In the present embodiment, a metal roller was used for the developing roller 20 , and its contact with the photosensitive drum 210 , which was rigid, was avoided according to the non-contact type developing method, with the gap at the narrowest point between the photosensitive drum 210 and the Development role 20 was set to 350 microns. However, the present invention is not directed to excluding the contact type development process in which the development roller 20 contacts the photosensitive drum 210 .

The development bias, with the DC voltage added as an offset to the AC voltage, specifically had a frequency of 1.0 kHz to 2.5 kHz, a peak-to-peak voltage Vpp of 1.8 kHz to 2.5 kHz, an offset voltage of -400 V to -550 V and a duty cycle of 30% to 50%. The AC waveform had a rectangular shape. The electric potential on the surface of the photosensitive drum 210 was -600 V, and the electric potential of the exposed latent image area was about -50 V.

In the experiment, the toner T is negatively charged by friction at a contact line of contact of the reset roller 10 and the developing roller 20 and fed using the reflection force as the electrostatic force and the mechanical force, thereby being absorbed on the devel opment roll 20th The toner T on the developing roller 20 , which is adsorbed in excess, can be regulated with the blade 30 . Then, as described above, the thickness of the toner layer TL is controlled by the factors such as the surface roughness Rz of the developing roller 20 , the blade (line) pressure Pb, the average volume particle diameter D of the toner T, and the charge amount q / m included, and it is variable in the range from a few µm to 100 µm.

The toner layer TL, which has been regulated to a predetermined thickness, is supplied to the developing area where the developing roller 20 and the photosensitive drum 210 are closest to each other. Subsequently, the toner T flows under the development bias toward an electrostatic latent image formed on the surface of the photosensitive drum 210 , and the latent image is made visible as a toner image.

The toner layer TL was based on the above ver search condition, and the effects that each condition has a condition of toner layer formation, and a Image quality is shown in Tables 2 to 7.

Table 2 shows the test results when the surface roughness of the developing roller 20 is provided with a constant value of 1 µm.

TABLE 2

With the relatively small surface roughness, even if the blade (line) pressure Pb is made lower, the toner layer thickness dt becomes thin, and therefore the image density becomes low. On the condition that the blade line pressure Pb was lowest (ie 11.0 gf / cm), the toner T escaped from the blade 30 . Accordingly, the line pressure blade Pb must have at least a load higher than 11.0 gf / cm.

A toner layer thickness dt that is less than 10 µm, would potentially result in unstable toner layer formation TL cause, which makes the image density low and uneven gets ugly. To achieve high quality printing, it is preferable to apply the toner layer thickness dt to the 1.5 times the average volume particle diameter D to put the toner.

Table 3 shows the test result when the surface roughness (average ten-point roughness) Rz of the developing roller 20 was constantly 5 µm. It has been found that a range of blade pressure Pb required to form a good toner layer TL can extend relatively far under this condition.

TABLE 3

Table 4 shows the test result when the surface roughness Rz of the developing roller 20 was constantly 8 µm. By this condition, similar to the above surface roughness Rz which was 5 µm, a good toner layer TL was obtained in a relatively wide range, but fog was more widespread than that of Rz of 5 µm. Since the image quality was good when the blade pressure was 93.9 gf / cm, a successive pressure test was carried out. As a result, blade fusion occurred after 8 hours. The blade fusion means that a blade and a toner generate the heat and the toner is melted by the heat and adheres to the blade. Because the excessive blade pressure Pb increases the load on the toner T.

TABLE 4

Table 5 shows the test result when the surface roughness Rz of the developing roller 20 was constantly 12 µm. When the surface roughness Rz was the highest, the result shows that the toner layer thickness dt tends to become thick, and fog was easily generated. The blade pressure Pb should be increased to limit the fog, but the increased blade pressure Pb would quickly cause the above fusion after some.

TABLE 5

Table 6 shows the test result when the developing roller 20 was able to stably form a toner layer having a uniform thickness and had a surface roughness Rz of 5 µm with the toner T having a relatively low charge. Due to the low-charged toner T, the toner layer thickness dt became thin and the image quality was low. When the blade pressure Pb was low at 11.0 gf / cm, the blade escaped an amount of toner similar to Table 3.

TABLE 6

Table 7 shows the test result when the developing roller 20 was able to stably form a toner layer of uniform thickness and had a surface roughness Rz of 5 µm with the toner T being relatively highly charged. Due to the highly charged toner T, the toner layer thickness dt became large, and fog tended to appear. Further, the blade 30 escaped an amount of toner because the toner had such a high electrical charge to strongly to the developing roller 20 to the other haf th. In words, the toner T had a high Refle xionskraft.

TABLE 7

The above test results are shown for Tables 2 to 5 in FIG. 2 and for Tables 6 and 7 in FIG. 3. In view of these relationships, the following equation 2 was able to determine the thickness dt of the toner layer TL on the developing roller 20 , the average volume particle diameter D of the toner T, the specific amount of toner charge q / m on the developing roller 20 , the average ten-point surface roughness Rz of the developing roller 20 and the Blade line pressure Pb herge.

dt = 1.8 × {q / m × Rz / (Pb-1)} ^1/2 × D ± 0.25D, 1.5D ≦ dt ≦ 3.5D (2)

In this case, 2 and 3 each point designated in FIG. Ver a search value, and from Equation 1, a solid line is derived. This equation is satisfied under the conditions shown in Table 8.

TABLE 8

Although in the present embodiment, the development roller 20 is made of aluminum and the blade 30 is made of stainless steel, both members can be selected from any electrically conductive rigid members. This is to prevent the blade 30 from floating electrically. Thus, blade 30 may alternatively be connected to another bias power supply, or only a surface of a non-conductive blade may be machined to be conductive. A similar effect would also be achievable if it were not made of metal but its surface was coated with a conductive resin. However, the blade 30 is preferably made from, for example, a leaf spring member and contacts the developing roller 20 (not at the end portion but at the middle section) to avoid damaging the developing roller 20 .

According to the toner film forming method and the aspect of an aspect of the present invention, it is possible to stably form a toner layer having a uniform thickness on the developing roller 20 under the conditions of Equation 2 using the metal developing roller 20 and the blade 30 , each of which can be manufactured with high processing accuracy and relatively low costs and can be provided with characteristically reliable stability. As a result, a reduced image density, increased fog in the non-image area, toner escaping the blade and toner fusion with the blade and a deteriorated toner charge due to the high load can finally be avoided, as a result of which images of high quality are obtained.

II. FORMING THE TONER LAYER BY CONTROLLING MECHANICAL PARAMETERS

The present inventors then discovered that formation of a toner layer having a uniform thickness mechanically depends (but is not limited to) on a blade shape and toner flow between the reset roller and the development roller, and have considered improving it. The conventional structure in which the metal development roller 20 and the metal blade 30 are used to form a toner layer includes, as described above with reference to Figs. 8 and 9, the rubber plate 2 b at a front end of the blade 2 after Understand that contact between the metal members could cause mutual damage and change their properties such as surface roughness. However, this would cause the toner agglomeration TB, which has a number of disadvantages, as described above.

In the present embodiment, it is proposed to replace the blade 30 with a blade 30 A shown in FIG. 4 or a blade 30 B shown in FIG. 5. Referring to Fig. 4 up to and including 6, a description follows of the blades 30 A and 30 B. Here, FIG. 4 is a partially enlarged sectional view of the blade 30 A and the developing roller 20 according to the present embodiment. Fig. 5 is a partially enlarged sectional view of blade 30 B and the developing roller 20 according to the present embodiment. FIG. 6 is a partial schematic cross section showing a state of a toner layer formed on the developing roller 20 using the blade 30 A of FIG. 4 and the blade 30 B of FIG. 5.

Although in Fig. 4 and the developing roller shown 5 20 both times made of aluminum, the present OF INVENTION is dung not directed to one or both of the devel opment roll 20, which are in Fig. 4 and 5, for For close when they come out Resin, etc., are formed.

The blade 30 A shown in FIG. 4 includes a rubber base 32 A as a pressure-applying portion which applies the predetermined blade pressure to the developing roller 20 and makes the thickness of the toner layer TL uniform, and a metal plate 34 A as a contact portion with the developing roller 20 . The plate 34 A is, for example, made of stainless steel, contains the end section 35 A, which has a sectional shape of an acute angle, a curvature or a curvature at its edge, so that a toner flow TF (shown with an arrow) between the reset roller 10 ( both not shown) and the development roller 20 cannot be blocked.

As a result, the blade 30 A can prevent the toner agglomeration TB and the cohesion of the toner T at its edge portion 33 A as shown in FIG. 8.

The plate 34 A is because it is made of metal, the rubber plate 2 b in terms of manufacturability, durability, strength and manufacturing costs. For example, it is difficult and expensive, a relatively small rubber plate 2 b in the form like a plate b manufacture 34th Furthermore, the rubber plate 2 b, which is acute-angled and round in section, would bend and be deformed in the direction of toner flow TF indicated by the arrow, thereby forming a new toner agglomeration and / or preventing the desired blade pressure from being applied to the development roller 20 becomes.

Optionally, the end portion 33 A of the base 32 A can also be cut at an acute angle, curved or rounded (ie, with a rounded edge) according to the plate 34 A like the end portion 33 B, which is described below. Preferably, such a central contact can be used with the plate 34 A that it contacts the development roller 20 not at the edge but at the middle section of the end section 33 B. This can prevent that the blade 30 A, the developing roller 20 beschä interred.

Similarly, the blade 30 B shown in Fig. 5, prepared as a member made of a metal base 32 B. The base 32 B includes the end portion 33 B, which has a sectional shape of an acute angle, a curvature or a curvature (ie, with a rounded edge) at its edge as the end portion 35 A. Since the base 32 B is made so that a toner flow TF (shown by an arrow) between the reset roller 10 (not shown) and the developing roller 20 cannot be blocked, the blade 30 B can increase the toner agglomeration TB and the cohesion of the toner T. at the end portion 33 B as shown in FIG. 8. The base 32 B is, since it is made of metal, the rubber plate 2 b superior in terms of manufacturability, durability, strength and manufacturing costs. Preferably, the base contact 33 A can come to the application where it contacts the development roller 20 not at the edge but at the main portion of the end portion 33 B, thereby preventing the blade 30 B from damaging the development roller 20 .

Both the blade 30 A and the blade 30 B used in the present embodiment, as shown in FIG. 6, can provide the uniform thickness dt of the toner layer on the developing roller 20 . For example, a laser scanning micrometer manufactured by Keyence Corporation can be used to measure uniformity. When the 30 A blade was used, the toner layer thickness dt was 18 ± 4 µm, while the toner layer thickness dt was 18 ± 2 µm when the 30 B blade was used. The average volume particle diameter of the toner is about 8 microns, while the thickness of the toner layer can preferably be 12 to 28 microns, better 16 to 20 microns; therefore, it is understood that a good thickness of the toner layer can be formed regardless of whether the blade 30 A or 30 B of the present embodiment is used.

A dispersion of the toner layer thickness is conventionally between ± 5-10 µm, while the present embodiment has a dispersion between ± 2-3 µm. If the surface roughness Rz of the developing roller 20 is 5 µm, if that of the blade 30 is less than 1 µm, generation of fine toner by pulverizing toner can be prevented, and fusion of the toner T on the blade 30 can also be prevented. As a result, the surface roughness of the blade 30 is preferably set to be smaller than that of the developing roller 20 . It is better if the surface roughness of the blade 30 is 1 µm or smaller, and that of the developing roller 20 can be 1 µm or larger.

As for the fusion, it was rated good when the developing roller idled for 20 hours without fusion. When the blade 30 with a surface roughness of 5 µm or more was used, fusion occurred after 2 to 3 hours. The pressure on the toner layer TL was 30 gf / cm. Even when the blade 30 with a surface roughness of 1 µm or less was used, the pressure of over 80 gf / cm resulted in the fusion within 5 hours. The blade pressure can be between 20 and 80 gf / cm, preferably between 30 and 60 gf / cm.

According to the developing device including the blade 30 A or 30 B and the developing roller 20 of the present embodiment, an end portion having an acute angle, curved or rounded end portion can maintain the toner flow, prevent the formation of the toner agglomeration, and a toner layer having a uniform thickness , Form stable on the development roller 20 . In addition, the developing device can prevent toner fusion on the blade by controlling the surface roughness of the developing roller 20 and the blade 30 and the blade pressure.

III. FORMING THE TONER LAYER BY CONTROLLING ELECTRICAL PROPERTIES OF NON-MAGNETIC AND SINGLE COMPONENT DEVELOPER

In the development process of the non-contact type, at that of the non-magnetic and one-component developer of present embodiment is used, the specific volume resistance of the toner attention dedicated. The present inventors have experimentally one completed picture developed (such a picture in which a entire printing area is completely filled), whereby trade usual or experimentally produced toner with ver  different resistance values is used, regardless whether the toner is the same in thickness layer and finally discovered that the Use the toner that has a certain resistance value has, when developing the non-contact type, black or, if printing with multiple colors, different colors Causes streaks in the paper feed direction PP, causing whose image quality is reduced. The current inventors he assumed that this occurred because the high resistance value of the toner to excessive charging of the toner and then causes an insulation breakdown gently, causing uneven printing such as a Streak is caused.

The developing conditions in this embodiment were as follows: the developing device 100 as shown in Fig. 1 was used, the reset roller 10 was made of urethane, the developing roller 20 was made of aluminum, the blade 30 was made of stainless steel, and the photosensitive drum 210 was from an OPC. The distance between the developing roller 20 and the photosensitive drum 210 was set to 350 µm. A rectangular voltage was applied to the reset roller 10 , the developing roller 20 and the blade 30 , which had a DC voltage of -550 V, a peak-to-peak voltage Vpp of 2.6 kV at a frequency of 2 kHz and a duty cycle of 35 % would have. The surface of the photosensitive drum 210 was uniformly charged to -600 V, and the electric potential in the latent image area reached -50 V by exposure.

In the process of manufacturing the non-magnetic and one-component toner used for the present embodiment form was used, 3.0% by weight to 6.0% by weight a pigment such as carbon black, 0.5% to 4.0% by weight an antistatic with a salicyl metal complex, etc., 1.0 wt .-% to 3.0 wt .-% of a wax with a  Polyethylene system as the main component to the polyesterbin the resin was added and then mixed, melted, kneaded and then pulverized and classified. The toner has run out produced by using toner matrices with a diameter of 6 to 10 microns, extracted from the powder produced were, with 0.5 wt .-% to 3.0 wt .-% silicon oxide and Titanium oxide, etc., which had been made hydrophobic when outer deposits were coated. A relationship between strips and the toners thus produced, one Having variety of resistance values became experimental clarifies.

The measurement of the resistance value of the toner and the calculation of a measurement error are now discussed below. Devices used were the dielectric loss measuring device TRS-10T (AS-31356: Ando Electric Co., Ltd.) and the granular electrode SE43 (AS-20646: Ando Electric Co., Ltd.). The toner measurement procedure follows the steps of forming toner into pellet form that is easy to measure, and then the resistance value of the pellet is measured. To form the shape of a pellet, a load of 600 kgf was applied to toner having a mass of 0.05 ± 0.002 g for one minute in a compressor molding machine having an inner diameter of 13 mm. The pellet thus formed was then measured using the above two devices. The resistance values measured by the above two devices were a capacitance Cx and a conductance Gx. The resistance value R (GΩ.cm) is calculated by the following equation 3. The measurement environment at the time of the experiment had a temperature of 24 ° C and a humidity of 28%.

R = A / (Gx.t) (3)

where A was a surface area of the pellet (1.33 cm ² ) and t was a thickness of the pellet.

Since the measurement error of the conductance Gx is represented by (± 5% of the actually measured Gx) + (measured frequency) × 3 × 10 ^-12 , the maximum resistance value R _max , if the measurement error is taken into account, can be expressed by equation 4.

R _max = A / (0.95 Gx- (measured frequency) × 3 × 10 ^-12 ) (4)

Fig. 7 shows the test result using the above devices under the above conditions. Fig. 7 shows a relationship between toner resistance values R and vertical stripes. It has been found that the toner with a resistance value R of 179 GΩ.cm or more, as shown in Fig. 7, would lead to vertical streaks when developing a filled image. Since at least the toner below 192 GΩ.cm does not produce a vertical streak if the above error is taken into account, it is preferable to use those toners which have a resistance value R below 192 GΩ.cm to improve the image quality.

It is not true that a low resistance value always improves the image quality since using toner with a lower resistance value (several GΩ.cm) than the toner 1 having the minimum resistance value in the present embodiment could cause poor transfer. whereby no high quality image could be obtained. Accordingly, the desirable resistance value R of the toner is at least between 10 GΩ.cm and 192 GΩ.cm without causing vertical streaks or poor transmission if the measurement error is taken into account.

According to the developer of the present embodiment can control the resistance value of the developer  excessive loading of the developer and a concomitant Prevent insulation breakdown.

IV. IMAGING DEVICE 200

As shown in FIG. 1, the image forming apparatus 200 of a typical embodiment of the present invention includes a developing device 100 , a photosensitive drum 210 , a precharger 220 , an exposure member 230, and a transfer roller 250 . The photosensitive drum 210 structurally has a photosensitive dielectric layer on a rotatable drum-shaped conductive holder and can be charged uniformly by the charger 220 . The photosensitive drum 210 is, for example, an OPC or an aluminum drum on which an organic photosensitive body with a separate function is applied in a thickness of about 20 µm, and the outer diameter is 20 mm, for example, and it rotates with one Rotation speed of 90 mm / s in the direction of the arrow.

The precharger 220 is a brush roller charger and uniformly charges the surface of the photosensitive drum 210 to about 600 V. Next, the exposure part 230 uses a laser beam to form an image on the photosensitive drum 210 that corresponds to a pressure source. Then, a state of charge in an area where an image is formed by the beam on the uniformly charged photosensitive drum 210 is neutralized and suppressed (e.g., to -50 V) by the action of the above conductive holder, and a latent one Image as an inverse pattern loaded to light and shadow of the document is formed. The latent image is made visible as a toner image by the developing device 100 .

In the developing device 100 , the developing roller 20 rotates in contact with the photosensitive drum 210 at the same rotation speed and in the same direction as the photosensitive drum 210 . The blade 30 regulates the toner T supplied by the reset roller 10 and forms a toner layer on the developing roller 20 . The developing device 100 of a typical aspect of the present invention, as described in some embodiments above, can stably form a toner layer having a uniform thickness on the developing roller 20 . The toner is negatively charged by the sliding friction between the reset roller 10 , the developing roller 20 and the blade 30 .

Thereafter, the toner which is present on the developing roller 20 in a layer which is applied to the developing roller 20 by the bias power supply 50 flows through the development bias, toward the surface of the photosensitive drum 210 and is adsorbed thereto. Toner that has not contributed to the development is scraped off by the rearward rotating reset roller 10 under the development roller 20 and is returned to the frame 40 via the lower part of the reset roller 30 . The toner image thus obtained on the photosensitive drum 30 is transferred on the transfer roller 240 to a printing paper which is fed in time along the feed path PP by feed rollers (not shown). The cleaner 250 collects the remaining toner on the photosensitive drum 210 . A paper with transferred print is then fed to a fixing part (not shown), fixed and finally ejected.

In the present invention, as explained above tert, preferred toner layer formation conditions for high quality imaging by measuring image quality effects under different development conditions the development role and the blade found out.

According to the toner layering method of the present the invention makes a change in shape and one Blade edge material possible, a uniform  Form toner layer, which improves the image quality is achieved.

It is also possible to get high quality images without vertical stripes by measuring and specifying wün to form appreciable toner resistance values.

Claims (19)

1. Developer stratification process with the following steps:
Loading non-magnetic and one-component developer, which has an average volume particle diameter D (µm), on an average specific charge q / m (µC / g);
Feeding the loaded developer to a development roller having a ten-point surface roughness Rz (µm); and
Form a layer of one-component developer with a layer thickness dt (µm) on the development roller by providing a blade in contact with the development roller at a blade line pressure Pb (gf / cm), where dt, Pb, q / m and D correspond to the following relationships:
4 ≦ D ≦ 12;
5 ≦ q / m ≦ 12;
1 ≦ Rz ≦ 12;
20 ≦ Pb ≦ 80;
dt = 1.8 x {q / m x Rz / (Pb-1)} ^1/2 x D ± 0.25D; and
1.5D ≦ dt ≦ 3.5D. 2. Development device with:
a development roller that has an average ten point surface roughness Rz (µm); and
a blade in contact with the developing roller at a blade line pressure Pb (gf / cm), through which a layer of a non-magnetic and one-component developer, which has an average volume particle diameter D (µm) and an average specific charge q / m (µC / g), can be formed on the development roller, the layer having a thickness dt (µm) and dt, Pb, q / m and D corresponding to the following relationships:
4 ≦ D ≦ 12;
5 ≦ q / m ≦ 12;
1 ≦ Rz ≦ 12;
20 ≦ Pb ≦ 80;
dt = 1.8 × {q / m × Rz / (Pb-1)} ^1/2 × D ± 0.25D; and
1.5D ≦ dt ≦ 3.5D. 3. Development device according to claim 2, wherein the development roller and the blade one each electrically have a conductive surface. 4. The developing device according to claim 2, further with a bias power supply that comes with the blade connected is. 5. The developing device according to claim 2, wherein the blade is made of a leaf spring, which with the Development role over a middle section of the blade in Contact is. 6. The developing device according to claim 2, wherein the development roller is made of metal and the blade is also made of Is metal. 7. Development device with:
a metal development role; and
a blade contactable with the development roller at a predetermined blade pressure to form a non-magnetic and one-component developer layer on the development roller,
in which the blade has a metal contact portion ent which is contactable with the development roller, which contact portion has a shape selected from a group consisting of acute-angled, curved and round shapes. 8. A developing device according to claim 7, wherein the contact portion of the blade has a surface roughness, which is less than a surface roughness of development role is. 9. A developing device according to claim 7, wherein an average ten point surface roughness of Blade is 1 µm or less and an average Development roller more than ten point surface roughness Is 1 µm. 10. A developing device according to claim 7, wherein the blade pressure is between 20 and 80 gf / cm. 11. A developing device according to claim 7, wherein the blade comprises:
an elastic resinous base to which the blade pressure is applied; and
a metal plate attached to the base and containing the contact portion. 12. Development device with:
a metal development role; and
a blade that is contactable with the development roller at a blade pressure of 20 to 80 gf / cm to form a layer of a non-magnetic and one-component developer on the development roller, in which the blade contains a metal contact portion that has a surface roughness that is smaller than that of the development role. 13. Non-magnetic and one-component developer, for a non-contact type development process Which developer can be used is a colored fine Particles and a fluidizing agent comprises and a speci fish volume resistance of more than about 10 GΩ.cm, but has less than about 192 GΩ.cm. 14. Container that has a non-magnetic and income component developer who is responsible for a development process Ren of the non-contact type is usable, which developer a colored fine particle and a fluidizing agent includes and a volume resistivity of more than about 10 GΩ.cm but less than about 192 GΩ.cm. 15. Image forming device with:
a photosensitive body;
a charger that charges the photosensitive body;
an exposure part which exposes the photosensitive body charged by the charger and forms an electrostatic latent image;
a developing device that develops the exposed photosensitive body and makes the electrostatic latent image visible as a toner image; and
a transfer part that transfers the toner image to a recording medium in which the developing device comprises:
a development roller with an average ten point surface roughness Rz (µm); and
a blade that is in contact with the developing roller at a blade line pressure Pb (gf / cm) and a layer of a non-magnetic and one-component developer that has an average volume particle diameter D (µm) and an average specific charge q / m (µC / g ) can form on the development roller, the layer having a layer thickness dt (µm) and dt, Pb, q / m and D corresponding to the following relationships:
4 ≦ D ≦ 12;
5 ≦ q / m ≦ 12;
1 ≦ Rz ≦ 12;
20 ≦ Pb ≦ 80;
dt = 1.8 x {q / m x Rz / (Pb-1)} ^1/2 x D ± 0.25D; and
1.5D ≦ dt ≦ 3.5D. 16. Imaging device with:
a photosensitive body;
a charger that charges the photosensitive body;
an exposure part which exposes the photosensitive body charged by the charger and forms an electrostatic latent image;
a developing device that develops the exposed photosensitive body and makes the electrostatic latent image visible as a toner image; and
a transfer part that transfers the toner image to a recording medium in which the developing device comprises:
a metal development role; and
a blade contactable with the developing roller at a predetermined blade pressure to form a layer of a non-magnetic and one-component developer on the developing roller, in which the blade includes a metal contact portion that is contactable with the blade, which contact portion has a shape, which is selected from a group consisting of acute-angled, curved and round shapes. 17. Imaging device with:
a photosensitive body;
a charger that charges the photosensitive body;
an exposure part which exposes the photosensitive body charged by the charger and forms an electrostatic latent image;
a developing device that develops the exposed photosensitive body and makes the electrostatic latent image visible as a toner image; and
a transfer part that transfers the toner image to a recording medium in which the developing device comprises:
a metal development role; and
a blade that is contactable with the development roller at a blade pressure of 20 to 80 gf / cm to form a layer of a non-magnetic and one-component developer on the metal development roller, the blade including a metal contact portion that has a surface roughness that is less than that is the role of development. 18. Imaging device according to any of the Claims 15 to 17, in which the development role of the photosensitive body is arranged separately. 19. Imaging device comprising:
a photosensitive body;
a charger that charges the photosensitive body;
an exposure part which exposes the photosensitive body charged by the charger and forms an electrostatic latent image;
a developing device that includes a developing roller that is separate from the exposed photosensitive body, from which developing roller a non-magnetic and one-component developer flies to the photosensitive body that has a volume resistivity of more than about 10 GΩ.cm but less than about Has 192 GΩ.cm, whereby the photosensitive body is developed and the electrostatic latent image is made visible as a toner image using the developer;
a transfer part that transfers the toner image to a recording medium; and
a container containing the non-magnetic and one-component developer.